216 Kleopatra
Encyclopedia
216 Kleopatra is a trinary main-belt
asteroid
that was discovered by Johann Palisa
on April 10, 1880, in Pola
. It is named after Cleopatra
, Queen of Ancient Egypt
.
Kleopatra has an unusual shape that has been compared to a dog's bone. This bilobate shape was revealed by adaptive optics
on the ESO 3.6 m Telescope at La Silla, run by the European Southern Observatory
. By bouncing radar signals off the asteroid, a team of astronomers at the Arecibo radio telescope
in Puerto Rico
were able to develop a more detailed computer model of its shape, which confirmed the earlier results.
Kleopatra is a relatively large asteroid, measuring 217 × 94 × 81 km. Calculations from its radar albedo
and the orbits of its moons show it to be a rubble pile, a loose amalgam of metal, rock, and 30–50% empty space by volume, likely due to a disruptive impact prior to the impact that created its moons.
and his collaborators announced that using the Keck Observatory's adaptive optics
system, they had discovered two moons
orbiting Kleopatra. The outer and inner satellites are about 5 km and 3 km in diameter, respectively.
In February 2011 they were named Alexhelios (ˌ, outer) and Cleoselene (ˌ, inner), after Cleopatra's children Alexander Helios
and Cleopatra Selene II.
It is believed that Kleopatra's odd shape, rotation, and moons are due to an oblique impact perhaps 100 million years ago. The increased rotation would have elongated the asteroid and caused Alexhelios to split off. Cleoselene may have split off around 10 million years ago. Thus Kleopatra may be a failed binary asteroid, very close to being a contact binary
.
Asteroid belt
The asteroid belt is the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets...
asteroid
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
that was discovered by Johann Palisa
Johann Palisa
Johann Palisa was an Austrian astronomer, born in Opava in Austrian Silesia .He was a prolific discoverer of asteroids, discovering 122 in all, from 136 Austria in 1874 to 1073 Gellivara in 1923...
on April 10, 1880, in Pola
Pula
Pula is the largest city in Istria County, Croatia, situated at the southern tip of the Istria peninsula, with a population of 62,080 .Like the rest of the region, it is known for its mild climate, smooth sea, and unspoiled nature. The city has a long tradition of winemaking, fishing,...
. It is named after Cleopatra
Cleopatra VII of Egypt
Cleopatra VII Philopator was the last pharaoh of Ancient Egypt.She was a member of the Ptolemaic dynasty, a family of Greek origin that ruled Egypt after Alexander the Great's death during the Hellenistic period...
, Queen of Ancient Egypt
Ancient Egypt
Ancient Egypt was an ancient civilization of Northeastern Africa, concentrated along the lower reaches of the Nile River in what is now the modern country of Egypt. Egyptian civilization coalesced around 3150 BC with the political unification of Upper and Lower Egypt under the first pharaoh...
.
Kleopatra has an unusual shape that has been compared to a dog's bone. This bilobate shape was revealed by adaptive optics
Adaptive optics
Adaptive optics is a technology used to improve the performance of optical systems by reducing the effect of wavefront distortions. It is used in astronomical telescopes and laser communication systems to remove the effects of atmospheric distortion, and in retinal imaging systems to reduce the...
on the ESO 3.6 m Telescope at La Silla, run by the European Southern Observatory
European Southern Observatory
The European Southern Observatory is an intergovernmental research organisation for astronomy, supported by fifteen countries...
. By bouncing radar signals off the asteroid, a team of astronomers at the Arecibo radio telescope
Arecibo Observatory
The Arecibo Observatory is a radio telescope near the city of Arecibo in Puerto Rico. It is operated by SRI International under cooperative agreement with the National Science Foundation...
in Puerto Rico
Puerto Rico
Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...
were able to develop a more detailed computer model of its shape, which confirmed the earlier results.
Kleopatra is a relatively large asteroid, measuring 217 × 94 × 81 km. Calculations from its radar albedo
Albedo
Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...
and the orbits of its moons show it to be a rubble pile, a loose amalgam of metal, rock, and 30–50% empty space by volume, likely due to a disruptive impact prior to the impact that created its moons.
Satellite system
In September 2008, Franck MarchisFranck Marchis
Franck Marchis , astronomer and planetary scientist, is best known for his discovery and characterization of multiple asteroids and its study of Io volcanism.The asteroid 6639 Marchis was named in his honor on April 4, 2007....
and his collaborators announced that using the Keck Observatory's adaptive optics
Adaptive optics
Adaptive optics is a technology used to improve the performance of optical systems by reducing the effect of wavefront distortions. It is used in astronomical telescopes and laser communication systems to remove the effects of atmospheric distortion, and in retinal imaging systems to reduce the...
system, they had discovered two moons
Asteroid moon
A minor planet moon is an astronomical body that orbits a minor planet as its natural satellite. It is thought that many asteroids and Kuiper belt objects may possess moons, in some cases quite substantial in size...
orbiting Kleopatra. The outer and inner satellites are about 5 km and 3 km in diameter, respectively.
In February 2011 they were named Alexhelios (ˌ, outer) and Cleoselene (ˌ, inner), after Cleopatra's children Alexander Helios
Alexander Helios
Alexander Helios was a Ptolemaic prince and was the eldest son of Greek Ptolemaic queen Cleopatra VII of Egypt and Roman triumvir Mark Antony. His twin was Cleopatra Selene II. He was of Greek and Roman heritage. Cleopatra named him Alexander in honour of her Macedonian heritage, and after her...
and Cleopatra Selene II.
It is believed that Kleopatra's odd shape, rotation, and moons are due to an oblique impact perhaps 100 million years ago. The increased rotation would have elongated the asteroid and caused Alexhelios to split off. Cleoselene may have split off around 10 million years ago. Thus Kleopatra may be a failed binary asteroid, very close to being a contact binary
Contact binary (asteroid)
In the study of asteroids, a contact binary is caused when two asteroids gravitate toward each other until they touch, forming an oddly-shaped single body. Asteroids suspected of being contact binaries include the unusually elongated 624 Hektor and the bilobated 216 Kleopatra and 4769 Castalia...
.
External links
- Bilobated shape of 216 Kleopatra
- Astronomers Catch Images of Giant Metal Dog Bone Asteroid – NASA article
- An Asteroid for the Dogs
- Orbital simulation from JPL (Java) / Ephemeris